Angioplasty is an established procedure for reducing the effect of atherosclerotic plaque on and intraluminal narrowing of the arterial walls within the vascular system of the patient. The effect is reduced by use of a catheter that is inserted into the site of the diseased-occluded vessel. A balloon portion of the catheter is then inflated to a predetermined pressure range and size, to radially compress the plaque occlusion, thereby increasing the internal diameter of the previously restricted artery. The balloon is then collapsed and the catheter is removed.
After the angioplasty procedure has been performed, as many as one-third to one-half of the patients soon develop restenosis. Restenosis can occur after angioplasty or other recannulation procedures, with or without stenting, wherein the migration and proliferation of benign cells cause a restenotic lesion to form, resulting in the further blockage of the intravascular structure.
Radiation is administered to patients for a variety of reasons, such as to treat restenosis, malignant or benign tumors, or the like. Examples of such treatments are disclosed in U.S. Pat. Nos. 5,059,166; 5,213,561; and 5,302,168.
A catheter system is known from U.S. Pat. No. 5,916,143 to Apple et al, and also from WO 99/12609, wherein an inert radioactive fluid such as a gas, like xenon-133, is delivered endovascularly to a treatment site in a patient, for treatment of restenosis after angioplasty, and for malignancies. When the catheter's balloon arrangement is inflated, it may include a plurality of discrete chambers for transporting the radiogas, and the catheter also includes a plurality of discrete chambers enabling substantial blood flow through the artery during treatment with the prescribed radiation.
Known xenon-133 single-balloon systems provide excellent shallow depth dose rates to 0.5 mm in easily handleable quantities in short treatment times. However, higher activity quantities or greater treatment times are required to obtain deeper depth dose profiles and could then create too high a surface dose without balloon wall thickening to screen out lower energy electrons.
Another form of radiation treatment utilizes seed or wire systems, such as those having iodine-125 or utilizing iridium-192. One such brachytherapy source wire is disclosed in U.S. Pat. No. 5,141,487 in which a source wire comprises iridium-192/platinum wire within a platinum sheath. Another is described in WO 00/04953, in which a brachytherapy device is a needle that is adapted to implant into a patient, seeds comprising an iridium-192/platinum alloy encased within plastic.
Known iodine-125 sources are not made to activity levels that are high enough for, or that are practically designed for, short term high dose rate brachytherapy for vessels or non-solid organs. They are inherently poorly centered and non-conformal in a thin catheter. At millimeter tissue distances, it does not provide higher needed shallow dose rates although providing better deeper dose rates for complete target minimal dose coverage.
It is desired to provide a radioactive source treatment system that is particularly suitable for endovascular use in larger arteries, for use with large diameter lumen catheters, and also that is useful for treatment of larger hollow cavity organ sites.
It is also desired to maintain limited treatment times, limited radioactivity quantities and controllable, variable-depth doses and dose rates for different sites.